Analytical Model Based on a Cylindrical Geometry to Study RF Ablation with Needle-Like Internally Cooled Electrode

Abstract

Radiofrequency (RF) ablation with internally cooled needle-like electrodes is widely used in medical techniques such as tumor ablation. The device consists of a metallic electrode with an internal liquid cooling system that cools the electrode surface. Theoretical modeling is a rapid and inexpensive way of studying different aspects of the RF ablation process by the bioheat equation, and the analytical approach provides an exact solution to the thermal problem. Our aim was to solve analytically the RF ablation transient time problem with a needle-like internally cooled cylindrical electrode while considering the blood perfusion term. The results showed that the maximal tissue temperature is reached 3mm from the electrode, which confirms previous experimental findings. We also observed that the temperature distributions were similar for three coolant temperature values (5 °C, 15 °C, and 25 °C). The differences were only notable in temperature very close to the probe. Finally, considering the 50 °C line as a thermal lesion mark, we found that lesion diameter was around 2cm, which is exactly that observed experimentally in perfused hepatic tissue and slightly smaller than that observed in nonperfused (ex vivo) hepatic tissue. Copyright © 2012 Juan A. Lpez Molina et al.